Whether insisting on the guilt of a murder suspect after seemingly befriending him or moving next door to Sarah Palin’s house for a most unauthorized biography, McGinniss was unique in his determination to get the most inside information, in how publicly he burned bridges with his subjects and how memorably he placed himself in the narrative.

McGinniss, the adventurous and news-making author and reporter who skewered the marketing of Richard Nixon in “The Selling of the President 1968” and tracked his personal journey from sympathizer to scourge of convicted killer Jeffrey MacDonald in the blockbuster “Fatal Vision,” died Monday at age 71.

McGinniss, who announced last year that he had been diagnosed with inoperable prostate cancer, died from complications related to his disease. His attorney and longtime friend Dennis Holahan said he died at a hospital in Worcester, Mass. Optimistic almost to the end, he had for months posted regular updates on Facebook and Twitter, commenting on everything from foreign policy to his health.

The tall, talkative McGinniss had early dreams of becoming a sports reporter and wrote books about soccer, horse racing and travel. But he was best known for two works that became touchstones in their respective genres – campaign books (“The Selling of the President”) and true crime (“Fatal Vision”). In both cases, he had become fascinated by the difference between public image and private reality.

McGinniss was a columnist for The Philadelphia Inquirer in 1968 when an advertising man told him he was joining Hubert Humphrey’s presidential campaign. Intrigued that candidates had advertising teams, McGinniss was inspired to write a book and tried to get access to Humphrey. The Democrat turned him down, but, according to McGinniss, Nixon aide Leonard Garment allowed him in, one of the last times the ever-suspicious Nixon would permit a journalist so much time around him. Garment and other Nixon aides were apparently unaware, or unconcerned, that McGinniss’ heart was very much with the anti-war agitators the candidate so despised.

The Republican’s victory that fall capped a once-unthinkable comeback for the former vice president, who had declared six years earlier that he was through with politics. Having lost the 1960 election in part because of his pale, sweaty appearance during his first debate with John F. Kennedy and aware of his reputation as a partisan willing to play dirty, Nixon had restricted his public outings and presented himself as a new and more mature candidate.

McGinniss was far from the only writer to notice Nixon’s reinvention, but few offered such raw and unflattering details. “The Selling of the President” was a sneering rebuttal to Theodore H. White’s stately “Making of the President” campaign books. It revealed Nixon aides, including Roger Ailes, disparaging vice presidential candidate Spiro Agnew, drafting memos on how to fix Nixon’s “cold” image and debating which black man – only one would be permitted – was right for participating in a televised panel discussion.

Historian David Greenberg wrote in “Nixon’s Shadow,” published in 2003, that McGinniss “sneaked in under the radar screen, presenting himself to Nixon’s men as such an insignificant fly on the wall that they never thought to swat him away.”

“If White was the voice of the liberal consensus, with its sonorous even-keeled wisdom,” Greenberg wrote, “McGinniss was an emissary from the New Journalism, with his countercultural accents, youthful iconoclasm, and nonchalant willingness to bare his left-leaning political views.”

Ailes, the chairman and CEO of Fox News, issued a statement Tuesday saying that McGinniss would “be remembered as a talented man.”

“He changed political writing forever in 1968,” said Ailes, who knew McGinniss for nearly 50 years. “We differed on many things, but he had a good heart. My prayers are with his family.”

“The Selling of the President” was published in 1969, spent months on The New York Times’ best-seller list and made McGinniss an eager media star. He quit the Inquirer and followed more personal interests. He wrote a novel, “The Dream Team,” and the idiosyncratic “Heroes,” a memoir that told of the breakup of his first marriage and romance with his eventual second wife, Nancy Doherty, and his failed quest for role models, among them author William Styron and Democratic Sen. Edward Kennedy.

In 1979, he was a columnist for the Los Angeles Herald-Examiner when an argument without end was born: McGinniss was approached by MacDonald, a fellow California resident, about a possible book on the 1970 killings for which the physician and former Green Beret was being charged.

In the early hours of Feb. 17, 1970, MacDonald’s pregnant wife and two small children were stabbed and beaten to death at the family’s home in Fort Bragg, N.C. The date, location and identities of the victims are virtually the only facts of the case not in dispute.

MacDonald, who sustained a punctured lung and minor injuries, had insisted that the house was overrun by a gang of drug-crazed hippies that chanted slogans such as “Acid is groovy” and spelled “PIG” in blood on a bedroom wall, a murderous rampage seemingly inspired by the then-recent Charles Manson killings.

But investigators suspected otherwise, believing that MacDonald killed his family and arranged the apartment to make it appear others had committed the crime. MacDonald was initially cleared of charges, then indicted, then finally brought to trial in 1979. He was found guilty and sentenced to three consecutive life terms.

“Fatal Vision,” published in 1983, became one of the most widely read and contested true crime books. McGinniss wrote not just of the case but of his own conclusions. He had at first found MacDonald charming and sincere but came to believe he was a sociopath who’d committed the killings while in a frenzied state brought on by diet pills.

McGinniss’ findings weren’t welcomed by MacDonald or by some fellow journalists. MacDonald sued in 1987, alleging McGinniss had tricked him by pretending to believe in his innocence, and he received an out-of-court settlement of $325,000. New Yorker writer Janet Malcolm cited McGinniss as a prime case of the reporter as a “kind of confidence man, preying on people’s vanity, ignorance, or loneliness, gaining their trust and betraying them without remorse.”

McGinniss wrote in his defense: “The attempt to manipulate through `cons and lies’ was – it seems clear to me now in retrospect – something Jeffrey MacDonald engaged in with me. Appearance of the book was forceful proof he had not succeeded.”

While MacDonald remained in prison, insisting on his innocence, the case was revisited in books, essays and opinion pieces. Jerry Allen Potter and Fred Bost defended MacDonald in “Fatal Justice,” published in 1997. Filmmaker Errol Morris, a MacDonald backer, came out with the book “A Wilderness of Error: The Trials of Jeffrey MacDonald” in 2012.

McGinniss hoped to have the last word with the e-book “Final Vision.”

“Jeffrey MacDonald was convicted of the murders of his wife and two young daughters in 1979,” McGinniss said in 2012. “In all the years since, every court that has considered the case – including the United States Supreme Court – has upheld that verdict in every respect. MacDonald is guilty not simply beyond a reasonable doubt, but beyond any doubt.”

McGinniss, who had been working on a book about his illness, wrote openly about his personal and professional follies and setbacks, whether cheating on his first wife or helping himself to the gourmet crabmeat in Styron’s kitchen. He struggled financially at times and battled depression and alcohol abuse. A 1993 biography of Sen. Kennedy, “The Last Brother,” was widely ridiculed for including invented dialogue.

None of his latter books approached the popularity of “Fatal Vision” or such other crime works as “Cruel Doubt” and “Blind Faith.” He returned a $1 million advance to write a book on the O.J. Simpson murder trial, expressing disgust that the former football star had been acquitted.

But by the 21st century he had cleaned himself up. He was an enthusiastic commentator on Facebook, posting regular updates about his health and current events. And he was back in the news, if not on the best-seller lists, with a biography of Palin, “The Rogue,” which failed to sell many copies despite allegations of drug use and a premarital fling Palin had with basketball star Glen Rice. The real headlines were in the reporting: Anxious for a close look into Palin’s world, McGinniss scored a front-row seat when he rented a house next door to her in Wasilla, Alaska.

“At first, Sarah will probably be less than thrilled to learn I’m here,” McGinniss wrote in the 2011 book’s introduction. “And who can blame her? Nonetheless, once she understands that I’m not here to hassle her, or to invade her family’s privacy in any way, maybe we can become, if not friends, then at least reasonably cordial summer neighbors.”